Now, extend the arms out.
Elbows straight.
Hands in fists. Put some power into your fists.
Elbows over Knees. This is extremely important. Elbows over KNEES.

Drop the shoulders, but at the same time do NOT let the small of your back unstick from the wall.

Now, slowly lower your spine straight down, still pressing the small of the back to the wall.
It should feel like someone's pulling you forward, but at the same time you're pulling yourself back. This is the foward/backward contradictory force part of the excercise